The present invention relates to a camshaft phase changing device and more particularly to a camshaft phase changing device for varying the timing of the valve actuation by an engine driven camshaft.
It is known in the art relating to engine valve gear to provide various means for varying valve timing as desired for the control of engine performance and efficiency. Among the various types of variable valve timing devices there have been employed camshaft phase changing devices, often in the form of drive pulleys or sprockets incorporating phase changing means for varying the phase between drive and driven members. Among the pertinent prior art, there are mechanisms having splined pistons that are hydraulically actuated against a return spring to vary the phasing of outwardly and inwardly engaged drive and driven members. Such arrangements are shown for example in U.S. Pat. Nos. 5,163,872 to Niemiec et al. and 5,119,691 to Lichti et al.